As I said earlier the Saito 65,80, 91 all have the same mounting dimensions, but I forgot to include the 100. Believe it is the same also. If a person is experienced enough to control the extra power then it's just a matter of how much $ to spend. If they are still learning I would suggest picking up a good used smaller engine then make the plunge later. Remember, the faster they fly the faster and easier they crash!!!! An important point to always remember.